Gadolinium (Gd)

Gadolinium (symbol Gd) is the chemical element with atomic number 64: a lanthanide (rare earth), solid at 0 °C, with an atomic mass of 157.25 u. Discovered in 1880 (Jean Charles Galissard de Marignac).

Gadolinium has seven unpaired electrons in its 4f shell, the most possible, which makes it an exceptional atomic magnet. Wrapped in protective molecules, it serves as a contrast agent in tens of millions of MRI scans every year. It is also the stable element that captures neutrons best.

Key facts

Atomic number: 64
Symbol: Gd
French name: Gadolinium
Atomic mass: 157.25 u
Molar mass: 157.25 g/mol
Family: Lanthanides
Position: period 6, f-block
State at 0 °C: Solid
Melting point: 1,311.9 °C
Boiling point: 2,999.9 °C
Density: 7.9 g/cm³
Electronegativity (Pauling): 1.2
First ionization energy: 593 kJ/mol
Atomic radius: 180 pm
Electron configuration: [Xe] 4f⁷ 5d¹ 6s²
Abundance in Earth's crust: 6.2 ppm (41st most abundant element)
Indicative price: 29 $/kg (order of magnitude)
Radioactive: no
Discovery: 1880, Jean Charles Galissard de Marignac

Origin of the name

Named after the Finnish chemist Johan Gadolin.

What does gadolinium look like?

A malleable, silvery-white metal that tarnishes slowly in air. A magnet will attract it… as long as the room is a little cool.

Where is gadolinium found?

About 6 ppm of Earth's crust. It occurs in monazite, bastnäsite and gadolinite. Traces of medical origin are now detected in rivers and in the tap water of some major cities.

Natural sources

Monazite
Bastnäsite
Gadolinite
Xenotime

How is gadolinium produced?

Separated by solvent extraction or ion exchange, then reduced to metal from its fluoride with calcium.

Top producers

China
Myanmar
Australia

What is gadolinium used for?

MRI contrast agents.
Neutron absorber in reactors and shielding.
Neutron detection: Japan's Super-Kamiokande detector has been doped with it since 2020.
Experimental magnetic refrigeration (the magnetocaloric effect).
X-ray screens and scintillators.

In everyday life

A contrast-agent injection during an MRI
An X-ray intensifying screen

Role in living things

No biological role. The free gadolinium ion is toxic, which is why it is locked inside “cage” molecules (chelates) that the kidneys clear within a few hours.

Hazards of gadolinium

In patients with kidney failure, some contrast agents have caused a serious disease, nephrogenic systemic fibrosis. Small amounts are also known to lodge long-term in the brain and bones; several agents were pulled from the European market in 2017.

Cosmic origin

Neutron stars: Created when two neutron stars collide — the “forge” of gold.
Dying stars: Made slowly in red giants (stars like the Sun at the end of their lives).

History of gadolinium

The Swiss chemist Jean Charles Galissard de Marignac spotted it by spectroscopy in 1880; Lecoq de Boisbaudran isolated its oxide in 1886. It was named after gadolinite, itself named in honor of the Finnish chemist Johan Gadolin, a pioneer of rare-earth research.

Did you know?

Its Curie temperature is about 20 °C: it is ferromagnetic in a cool room and loses its magnetism in a warm hand.
Gadolinium-157 captures neutrons tens of thousands of times more efficiently than most elements.
The Rhine and the Spree carry a measurable excess of gadolinium from hospitals.

Isotopes of gadolinium

Gadolinium has six stable isotopes plus a seventh, gadolinium-152, that is very weakly radioactive. Gadolinium-157 holds the all-time record for neutron capture among stable isotopes.

gadolinium-152: 0.2% of natural gadolinium, radioactive, half-life 1.08 × 10¹⁴ years
gadolinium-153: radioactive, half-life 240 days. A radiation source for measuring bone density and calibrating medical cameras.
gadolinium-154: 2.18% of natural gadolinium, stable
gadolinium-155: 14.8% of natural gadolinium, stable
gadolinium-156: 20.47% of natural gadolinium, stable
gadolinium-157: 15.65% of natural gadolinium, stable. The champion of neutron capture: used to control reactors and to detect neutrinos.
gadolinium-158: 24.84% of natural gadolinium, stable
gadolinium-160: 21.86% of natural gadolinium, stable

Related elements

Same family (lanthanides): Lanthanum (La), Cerium (Ce), Praseodymium (Pr), Neodymium (Nd), Promethium (Pm), Samarium (Sm), Europium (Eu), Terbium (Tb), Dysprosium (Dy), Holmium (Ho), Erbium (Er), Thulium (Tm), Ytterbium (Yb), Lutetium (Lu).